Neurological disorders are prevalent in the United States and around the rest of the world, with millions of people suffering from various types of neurological disorders of varying severity. A person who has a neurological disorder may be substantially debilitated, and may experience a significant decline in quality of life.
One example of a neurological disorder is epilepsy, which is characterized by the occurrence of seizures. Because epilepsy is characterized by seizures, its sufferers can be limited in the kinds of activities in which they may participate. For example, an epileptic may have limited or no ability to drive, work, or participate in recreational activities. Some epilepsy sufferers have serious seizures with such high frequency that they are effectively incapacitated. Additionally, in some cases, epilepsy is progressive, and can be associated with degenerative disorders and conditions. Over time, epileptic seizures may become more frequent and serious, and in particularly severe cases, may lead to the deterioration of other brain functions, as well as physical impairment.
Drug therapy and surgery are examples of current methods that may be used to treat epilepsy. Various antiepileptic drugs are available, and may be administered, for example, at the onset of pre-seizure symptoms or auras, to mitigate the effects of epilepsy. Surgical procedures include radical surgical resections, such as hemispherectomies, corticectomies, lobectomies and partial lobectomies, as well as less radical procedures, including lesionectomies, transections, and stereotactic ablation. An additional procedure that may be used to treat epilepsy is electrical stimulation, in which seizures may be treated and/or terminated by applying electrical stimulation to the brain. Typically, the detection and responsive treatment of seizures via electrical stimulation can include analysis of electroencephalogram (EEG) waveforms and electrocorticogram (ECoG) waveforms. An EEG waveform includes signals representing aggregate neuronal activity potentials detectable via electrodes applied to a patient's scalp, and/or signals obtained from deep in a patient's brain via depth electrodes and the like. An ECoG waveform includes signals obtained from internal electrodes near the cortex of the brain (generally on or under the dura mater), and/or brain signals from deeper structures.
Generally, it is preferable to detect and treat a seizure at or near its inception, or even before it has begun. The beginning of a seizure, or an onset, may be a clinical onset or an electrographic onset. A clinical onset represents the beginning of a seizure as manifested through observable clinical symptoms, such as involuntary muscle movements or neurophysiological effects such as lack of responsiveness. An electrographic onset, which typically occurs before a clinical onset and which may enable intervention before the patient suffers symptoms, refers to the beginning of detectable electrographic activity indicative of a seizure.
Epilepsy is only one example of a neurological disorder. Additional examples of neurological disorders include movement disorders (e.g., Parkinson's disease), psychiatric disorders, sleep disorders, and language disorders. As briefly discussed above, these and other neurological disorders can severely disrupt a person's quality of life. Thus, it would be preferable to provide devices and methods that may be used to provide drugs and/or other bioactive agents to a target site to treat a neurological disorder.